Apparatus for forming glass-ceramic articles

ABSTRACT

A method and apparatus for making a one-piece, cored glass article of substantial mass and having a complex configuration, by forming a glass-ceramic making material in molten state in a four-part mold having opposed members in pairs juxtapositioned and cooperating collectively to form a cored molding cavity. The closed and clamped mold includes an upper loading opening into which a pressing plunger is manipulated for pressing the material. The said material is of about 3 poise viscosity or less as it is loaded into the mold. The molten glass is pressed in the cored mold to fill the complex cavity and define the configuration of the article. Thereafter, during cooling the glass, the pressure on the glass is reduced by sequentially withdrawing the plunger and one or more of the mold faces and core sections to compensate for the difference in coefficient of expansion in the heat exchange between the contracting glass (undergoing cooling) and the expanding mold (undergoing heating). The faces of the opposed mold members are backed off from the hardening glass progressively. The formed glass liner article is cooled so as to prevent cracking, removed from the mold and inspected. Surplus inner and exterior segments of the article are then finished by drilling, cutting and grinding. The &#39;&#39;&#39;&#39;green glass&#39;&#39;&#39;&#39; article, partially mechanically finished, is then converted to a glass-ceramic material by heat treatment, and then given final finishing. In the apparatus, a massive metal bed supports two pairs of opposed mold faces, comprised of a pair of end mold members and a pair of side mold members. The end mold members are movable longitudinally along the bed toward and away from each other and the side mold members are movable laterally of the bed toward and away from each other. The side mold members are pivotably mounted for juxtaposed positioning on the bed; the end molds are movable longitudinally along a track in the bed bottom for juxtaposed positioning cooperating with the side mold members to define a cored mold cavity for forming a one-piece article of glass. A pair of hand cranks and turn screws, mounted on each end of the bed, propels the end mold members on the bed. A closure member positioned about the top of the end members defines the loading aperture for the mold and locks the closed mold members in molding or forming position during the pressing operation.

United States Patent [191 June 25, 1974 Pei [ APPARATUS FOR FORMINGGLASS-CERAMIC ARTICLES [76] Inventor: Yu K. Pei, 3849 S. BeverlyHillsDL, Toledo, Ohio 43614 [22] Filed: July 27, 1973 [21 Appl. No.:383,121

[52] v US. Cl 65/357, 65/359, 65/360,

, a 65/361 [51] Int. Cl........' C03b 9/00 [58] Field of Search 65/361,359, 360, 358, 65/357 Related.Utst Aep ati n Da e. [62] Division orser.No. 267,006,.lune 28, 1972, Pat. No. 3,809,599 which is acontinuation-in-part of Ser. No.

5 1 91 9 ,71tab 0nei a-..

[56] References Cited 7 UNITED STATES PATENTS 405,863 6/1889 Atwater etal. 65/359 X 768,034 8/1904 Colburn 815,037 3/1906 Philippoteaux1,674,996 6/1928 Schmunk 1,674,997 6/1928 Schmunk 2,217,140 10/1940Smith 6 5/357 Primary Examiner-Frank W. Miga Attorney, Agent, or FirmJ.R. Nelson; E. J. Holler [57] ABSTRACT ity. The closed and clamped moldincludes an upper loading opening into which a pressing plunger ismanipulated for pressing the material. The said material is of about 3poise viscosity or less as it is loaded into the mold. The molten glassis pressed in the cored mold to fill the complex cavity and define theconfiguration of the article. Thereafter, during cooling the glass, thepressure on the glass is reduced by sequentially withdrawing the plungerand one or more of the mold faces and core sections to compensate forthe difference in coefficient of expansion in the heat exchange betweenthe contracting glass (undergoing cooling) and the expanding mold(undergoing heating). The faces of the opposed mold members are backedoff from the hardening glass progressively. The formed glass linerarticle is cooled so as to prevent cracking, removed from the mold andinspected. Surplus inner and exterior segments of the article are thenfinished by drilling, cutting and grinding. The green glass article,partially mechanically finished, is then converted to a glass-ceramicmaterial by heat treatment, and then given final finishing. In theapparatus, a massive metal bed supports two pairs of opposed mold faces,comprised of a pair of end mold members and a pair of side mold members.The end mold members are movable longitudinally along the bed toward andaway from each other and the side mold members are movable laterally ofthe bed toward and away from each other. The side mold members arepivotably mounted for juxtaposed positioning on the bed; the end moldsare movable longitudinally along a track in the bed bottom forjuxtaposed positioning cooperating'with the side mold members to definea cored mold cavity for forming a one-piece article of glass. A pair ofhand cranks and turn screws, mounted on each end of the bed, propels theend mold members on the bed.'A closure member positioned about the topof the end members defines the loading aperture for the mold and locksthe closed mold members in molding or forming position during thepressing operation.

9 Claims, 21 Drawing Figures PAIENIEUmzsmm sum 2 0r 9 FIG. IS"

PAIENIEBJW 3.819 352 sum 5 or 9 FIG. 9

1 APPARATUS FOR FORMING GLASS-CERAMIC ARTICLES This is a division of myearlier copending application Ser. No. 267,006, filed June 28, 1972; nowUS. Pat. No. 3,809,599 issued May 7, 1974, which is in turn acontinuation-in-part of Ser. No. 149,650 filed June 3, I971, nowabandoned. I

This invention relates to a method and apparatus for molding 'a coredglass article of complex configuration from a highly fluid glasscomposition. The method further includes annealing and finishing stepsperformed on the molded article. The preferred form of the inventionincludes the manufacture of a glass-ceramic gas turbine inner linerarticle in which the molded and annealed piece-is subsequently heattreated to transform the glass material to-a glass-ceramic.

DESCRIPTION OF THE PRIOR ART pensate for the differences in thecoefficient of thermal expansion between the glass and the metal mold.The differences of expansion occurs in the glass which is setting andcontracting and the mold, which is being heated by the glass andexpanding. It is an object of this invention to provide an apparatus andprocess for forming, as one piece, a glass article such as the gasturbine inner liner, from a molten glass material loaded to a mold at ornear 2,900F. and pressing the article therein as one piece, whilecompensating for the differences in coefficients of thermal expansionbetween the glass and mold without defects in the formed article. Thelatter is subsequently converted from a glass (green glass state) to aglass-ceramic state.

This invention enables forming a complex article such as a gas turbineinner liner from a glass-ceramic forming material. The process of thisinvention produces a superior article in that it obviates the need forforming several component parts to be subsequently joined mechanicallyinto an inner liner. Rather, the

and provide very desirable low expansion characteristics. A gas turbineis an apparatus for imparting a rotating motion to a shaft bycirculating and-expanding very hot gases through a plurality of turbineblades attached to the shaft. The inner container for the hot gases (on.the order of 2,0( )0F) is called an inner liner. Such hot environmentat the inner liner heretofore has required the use of special alloymetals which are costly, and these alloy metals possess positiveexpansion char acteristics in this degree of heat.

More recently, the gas turbine inner liner has been, experimentally atleast, constructed of a zero or negative expansion material havingrefractory characteristics, this material being a glass-ceramic ofrelatively low cost, such as disclosed more specifically hereinafter.

. Although the material proposed, e.g.- a glass-ceramic,

is basically a low cost material, the manner of forming this materialinto a massive, complex one-piece casting, as an inner liner, is aproblem specifically dealt with by the present invention. Slip castingis a probable manner by which this complex article may be molded and hasheretofore been utilized; however, this invention proposes a moreeconomical, a novel and'more reliable method for producing the desiredproduct of the glassceramic material.

SUMMARY or THE INVENTION an article such as a gas turbineinner linerfrom agla'ss which is solidified to a"green glass and then convertedinto a glass-ceramic material. The molten glass is placed in a specialforming mold and partially fills the confines of the complex cavity bygravity flow. Next, a

pressing plunger completely forms the glass in the cav-' ity and theplunger'is withdrawn. As the molten glass thereafter hardens totheconfiguration of the special mold, the special mold is opened byslightly withdrawing the mold members away from each other to compresentinvention forms a one-piece cast glass article that is rough cored andlater inspected, rough machined prior to heattreatment to convert theglass green glass into a glass-ceramic material of improved refractoryand expansion properties. The glassceramic piece may then be finished bygrinding and/or polishing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view ofthe mold apparatus of this invention;

FIG. 2 is an end elevational view of the apparatus taken from the lefthand side of FIG. 1;

FIG. 3 is a partial sectional elevational view taken along line -3- onFIG. 2;

FIG. 4 is a side elevational view of the forming section of theapparatus of FIG. 1, partly in section;

FIG. 5 is a perspective view of the apparatus of FIG. 1;

FIG. 6 is a top plan view of the forming mold of FIG. 1;

FIG. 7 is aside elevational view, partly in section, of the apparatus ofFIG. 6;

FIG. 8 is a view of the apparatus, like FIG. 6, showing the closuredevice;

FIG. 9 is a partial, longitudinal sectional view taken along line 9-9 ofFIG. 8;

FIG. 10 is a transverse sectional elevational view taken along line10-10 of FIG. 8;

FIG. 11 is a sectional elevational view like FIG. 10 showing the sidemold members in a pivoted, open position;

FIG. 12 is an elevational view of the forming apparatus, partly insection, illustrating the guide ways for the longitudinal movement ofthe end mold members along the bed;

FIG. 13 is a perspective view of the gas turbine inner liner glassarticle formed in the pparatus of the foregoing Figures;

FIGS. 14-17, inclusive, schematically illustrate the molding steps ofthe invention in which:

FIG. 14 shows the mold in closed position ready for loading;

FIG. 15 shows the mold loaded with a quantity of molten glass;

FIG. 16 shows the pressing of the glass by force of the plunger; and

FIG. 17 shows the glass formed in the mold just after the pressingplunger is withdrawn.

FIGS. 18-21, inclusive, schematically illustrate the finishing steps ofthe invention in which:

FIG. 18 shows the molded glass article after removal from the mold andillustrates the step of drilling a central cylindrical passagewaythrough the inner liner piece;

FIG. 19 shows the step of trimming the upper end of the inner linerpiece by removal of a portion of the glass, such as by sawing;

FIG. 20 shows the inner liner piece after trimming and finished exceptfor internal polishing or grinding; and

FIG. 21 shows the inner liner piece undergoing machining, such as bygrinding, one or more of the interior surfaces of the article.

DESCRIPTION OF THE INVENTION In prior art practices, gas turbine innerliners were formed from a number of separate individual parts, using aslip casting technique, and the formed parts were brought together andjoined by mechanical means, such as a frame, to form an inner liner.This invention provides a method and apparatus for forming articles suchas a hollow turbine inner liner by loading molten glass at about 2,900F.and glass viscosity of about log 3 or less, transferring the moltenglass into the mold of this invention, applying pressure to the moltenglass to distribute it about the cored configuration of the mold cavity,compensating for the differences in coefficients of thermal expansion ofthe molten glass and the hot mold parts, permitting the molten glass toharden, removing the formed liner article of solidified green glass andannealing such glass article by prescribed schedule (hereinafterdisclosed) to relieve stresses and avoid cracking of the piece.Next,-the piece is partially finished by machining certain areas to theshape of the final inner liner. The partially machine, annealed glass isthen converted to a glass-ceramic material by the additional heattreatment process steps described herein, and then finished by machiningto the desired dimensions.

A turbine is an engine for imparting a rotating motion to a shaft byconducting expanding hot combustion gases through a plurality of bladesattached to a rotatable power shaft. The turbine liner contains the hotgases; hence it operates in extremely hot temperature zones whichrequire special alloy metals, ceramics or glass-ceramic materials tocontain the expanding of hot gases.

This invention relates to an improved method of forming and finishingglass articles and converting same to a glass-ceramic which can containthe hot gases. The process or method provides for making the one-piecearticles such as described herein, repetitively in production.Additional advantages provided by this invention are: The formed articleis transparent, permitting the detection of flaws in the article priorto the additional expensive steps of annealing and conversion to aglass-ceramic material. The formed articles can be inspected while inthe glassy state and defective articles can be rejected prior to suchsubsequent steps of annealing and heat treatment conversion to an opaqueglass-ceramic, such early detection of defects resulting in costsavings.

MOLD APPARATUS Referring to the drawings, FIG. 1 is a side view of theapparatus 10. Four mold members, 11, 12, 13 and 14 (FIG. 6), arepositioned on massive metal bed 15. Side members 13 and 14 arepositioned on pivot shafts 24 disposed parallel to the bed 15 and arehingedly attached to the bed in pivoted relation to open and closemembers 13 and 14 transversely on bed 15. End members 11 and 12 aremovable longitudinally along bed 15 by opposedly operated hand cranks19. Hand cranks 19 each comprise a threaded shaft 20, journal mountedfor rotation in a bracket 21 on the bed frame 15. Mold members 11 and 12are each rigidly connected to an internally threaded collar 22. Eachthreaded shaft 20 is rotated by a crank and the threaded connection toits collar 22 imparts movement to the end member (11 or 12)longitudinally along bed 15. Each of the mold members 11 and 12 havehardened slides 66 that ride on parallel and inwardly inclined ways 45on bed 15.

The end mold members 11 and 12 cooperate to provide one of the importantand novel features of the invention, namely, the provision of mold coreelements 26 indicated specifically on FIGS. 3-5, 7, and 911 as 26a and26b, which oppose each other and define the interior web-like sectionsof the article shown on FIG. 13. As seen on FIG. 13, the interiorhorizontal wall 57 of piece 53 is formed between the upper core 26a and26b at the space 29 indicated on FIG. 5. The buttresses 58 of piece 53are formed by flat faced cut-outs shown at 260 on the upper coreelements 26a. Cylindrical barrel 54 and the base 54a are formed by theinterior semicircular facings of the upper core element 26a. The lowercontinuation 55 of barrel 54 is similarly formed by the interiorsemi-circular facings of the lower core element 26b. Thus, through coreelements on the end mold members, the interior structure of the moldedpiece 53, such as 54, 54a, 55, 57 and 58, is shaped. The interior of thebarrel 54 is shaped by a press plunger 49, to be presently described.

Side members 13 and 14 are hinged on bed 15 to pivot about pin 24. OnFIGS. 10 and 11, the side members are shown in their open and closedpositions, respectively, about the already closed end mold members 11and 12 just described. (See FIG. 5 whereat closing and opening movementof the side members is demonstrated as between the positions of 13((closed)) and 14 ((open)).

As shown on FIG. 2, positioning blocks 27 are an integral part of thebed. A key 28 fits into the block 27 and rigidly positions the endmembers against any turning movement, (FIG. 5). The two pairs of endmembers ll, 12 and side members '13, 14 cooperate in their closed,molding position to form a mold cavity 43. The side members each includea semi-annular, mouth defining, upper ring 16, which are complementaryand together in closed relationship define the mold loading passageway43a, (FIG. 3). As seen on FIG. 5, the mold apparatus is closed in thefollowing manner. End members l1 and 12 are moved toward each other to ajuxtaposed position along longitudinal ways 44. Next, the side moldmembers 13 and 14 are each pivoted toward each other to the closedposition about end members 11 and 12 whereat the side members overlapportions of the end members 11 and 12 in a closed position, (FIG. 7).Bed 15 has stops 32, and the mold mounts 25 have flanges 59, which abutthe stops when the end mold members are in their forming position. Thecombined action of the key 28 and the positioning block 27, inconjunction with the abutting relationship between thebed and the endmold members 11'andl2 provide a very rigid positioning'of the moldmembers during the molding process, which aids to insure dimensionalaccuracy of the finished article, d

The mold sections are locked and held in molding position by thecombination of the opposed end cranks 19, which place endmembers 11 and12 into position, the closing of side members 13 and 14', which wrap.around or envelope apor'tion of the structure of 1 1 and 'so thattheir. upper neck sections 16 abut one another,

the device 18 encircles the top part of the sections and 6 and the innersurfaces of the side faces in the molding position. Inner edge 39 of theside mold member's engages the circumference of the forming section 26of the end members in forming position.

' For a more convenient illustration, FIGS. and 11 respectively show theside mold members in their closed position and in their open position.The members l3 and 14 pivot between these positions about their hingepins 24 and hinges 23.

Side mold members 13 and 14 swing outwardly from fthe end center line ofthe bed, the inner wall of the is closed tightly to clamp about flange16a. The mold tionon the flange 16a of the necksection'. 1

As may be seenon FIG. 3, the end mold members 11 and 12are each made ofa massive piece of metal, comprising a mount 25 and forming elements 26which, in

their complementary shape, define the cored portion and part of theexterior. configuration ofthe turbine inner liner piecethat is to beformed. The forming elements 26 comprise cores 26a and 26b and the outerannular surface 38 of elements 26 are inwardly tapered for purposes ofmating inpartwith the round surfaces of side mold members '13 and 14along their inner surfaces and for withdrawal or removal of the elements26 from a molded glass piece (see FIG. 3). Mount 25 has web plates 46strengthening the mold member mount.

Bottom surface 60 of mount 25 rests on the bottom it track 44-of bed 15.As is clearly shown on FIGS. 3 and 12, the bed is U-shaped with bottomtrack 44 having I arcuate ways on-sides 40. The lowersurface of -mount25 has a complementary arcuate, shape to nest on the ways surface oftrack 44. This relationship provides a true longitudinal movement oftheend mold members attached to mounts 25 asthey are oppositely moved bycranks 19 along bed 15. Mount 25 has a longitudinal tongue 66, whichrides in groove 65 along the track 44.

This tongue and groove fit maintains the radial alignment of the members11 and 12 on the track 44.

Referring to FIGS. 3 and 4, eachcomplementary mold member 13 and 14Vincludes a-molding surface forming a portion of the exterior of thepiece 53 molded therein. The top, middle and bottom side fonningsurfaces 35,36 and 37, respectively, form the upper arcuate surface 53a,flat side surface 56 and lower arcuate surface 53b of the piece53 (FIG.1-3).

The annular surfaces 39 seat on the tapered surface 38of formingelements 26 offend'mold members 13 and 1.4. The left-hand portion ofFIG. 3 illustrates the end mold member. 11 and side mold member 13in theclosed' forming position. In the right-hand portion of FIG. 3,mold'member 12 is shown in a partially open position. When this moldsection is closed, the annular abutment-'31 will seat against thesurface 30 of the upper neck section 16 of the side members and theinterior vertical faces of cores 26 will engage. There is molding spaceat62 between the tapered surface 38 mold sections parting along surfaces45 and 56 on each. The hinge lugs 47 abut against the stops 48 toposition movable sections of 13 and 14 in an open position (FIG. 11).

The four mold members are designed to form a cavity 43 to contain moltenglass, and to have the glass flow into the cavity in a turbulent-freeflow. The cavity 43 contains forming cores 26 to shape the glass to anarticle 53 shown on FIG. 13, (shown in phantom on FIG. 11). The glasscomposition in molten state, as hereinafter disclosed, is poured intothe mold through the opening 43a in the neck sections 16. Afterintroducing the molten glass charge, pressing plunger 49 is insertedinto the mold. cavity. Pressing, plunger 49 is inwardly tapered andexerts a'pressure on the entrapped molten glass as the plunger is driveninto the mold cavity 43 andforces the glass throughout the closed moldcavity. A drive apparatus 51 of any conventional type may be used toreciprocally operate the plunger, and is thereforeshown only in arepresentative manner herein. The formed turbine liner 53 has theconfiguration of the mold cavity 43 and the complicated article 53 isformed in one piece by pouring molten glass into the mold and applyingvariable pressures to the glass. The fonning process of this inventionwill be presently described. i

The molding sequence of the apparatus is shown on FIGS. 7 and 9-11. Withthe mold closed, as shown on FIG. 7, molten glass is loaded into thecavity. Next the pressing plunger 49 is inserted into the molten glasscharge, to press the molten glass and fill the convolutions of the mold(FIGS. 9 and 10). After the glass is initially pressed to shape by theplunger, the latter is withdrawn and the mold members 11-12 are eachrelaxed from the molding position to compensate for differentialexpansions/contractions of the metal and glass materials undergoing heatexchange as the glass cools. As is explained hereinafter, this relaxingof the pressing or forming pressure avoids cracking of the molded partas the glass cools and heat exchange takes place. After sufficientcooling of the glass part 53, the mold members are opened, as shown onFIG. 12, and the formed turbine inner liner53 (shown in phantom outline)is removed from the mold. The formed turbine inner liner piece 53 has anouter curved shell comprised of upper arcuate wall 53a, lower arcuatewall 53b joined by the flattened vertical side wall 56. A horizontalseparating wall 57 extends between the opposed vertical walls 56. Aplurality of buttresses 58 are formed between the separating wall 57 andthe inner surface of wall 56 of the piece 53. The cylindrical barrel 54extends vertically through upper wall 53a and wall 57. The barrel 55integral with upper barrel 54 extends toward the bottom cylindricalsection 52 formed by the mold bottom plug 33 in lower wall 53b (FIG.11). This lower portion 55 of the barrel has a passagedrilled throughthe wall 52 in the finishing operation. The plug 33 forms a removablebottom member for the mold.

FIG. 12 shows the bed 15 in cross-section with the side walls 40 and thetrack 44, and having groove 65 in the bottom of the bed. A tongue 66extends from the mount and is engaged in the groove. This arrangement oftongue 66 and groove 65 stabilizes the movement of the mount 25 alongthe bed track 44 and, in conjunction with the action of block 27 and key28 on the side of the mount, serves to rigidly position the opposed moldmember mounts on the bed.

PROCESS FIGS. 14-21 are schematic drawings illustrating the process offorming a one-piece glass-ceramic article such as a gas turbine innerliner 53. In carrying out the process, the mold members 11-14 are closedto the positions shown on FIG. 14. Prior to closing, the mold cavity 43may be coated with a release coating which can be a graphite compound, arefractory oxide coating, or the like. Molten glass at a temperaturehigher than about log viscosity 3 is poured into the mold through thetop opening 43a of the cavity 43 until the molten glass fills most ofthe cavity volume, as shown on FIG. 15. At log viscosity 3 or less, theglass is very fluid. A plunger 49 is inserted into the mold cavitythrough top opening 43a and glass pressing pressure, generated by thedriving mechanism 51, causes plunger 49 to press the viscous glassthroughout the mold cavity 43. This is shown on FIG. 16. The pressingpressure dwells momentarily as plunger 49 arrives at its innermostpenetration. The taper of the plunger 49 is conventional to permitwithdrawal. As plunger 49 is pressed into the molten formable glass inthe mold cavity, it forces the glass around the core elements 26 and theresultant piece 53 is shaped. With the glass mass distributed forcooling (FIG. 17), it is necessary to eliminate cracking of the piecewhich often occurs at its thicker sections. Thereafter, plunger 49 isquickly partially withdrawn and the glass undergoes some cooling in thecondition shown on FIG. 17. Although it is not illustrated precisely onthe drawings, in the condition shown on FIG. 17 the end mold members 11and 12 are also relaxed, i.e., slightly retracted. According to the timeschedule disclosed hereinafter in Table I, simultaneously, the moldcavity is expanded by backing off the end mold members 11 and 12; thesemold members being moved about Vs inch; then, subsequently, after a fewseconds, a second increment of 3 5 inch, etc. The step of backing offthe mold members from contact with the formed glass inner liner 53requires precise compensation for both the contracting molten glass andthe expanding hot metal mold members. The quick removal of the plunger49 and separation of the end mold members prevent the expanding metalmold from cracking the cooling liner, due to the different expansionrates of the glass and metal materials. This occurs when the glass inthe mold has cooled sufficiently to be self supporting. Thereafter, sidemold members 13 and 14 are swung open, and end mold members 11 and 12are completely withdrawn. The molded article is next transferred to alehr and cooled further, according to the schedule, to prevent cracking.In the annealing lehr, the liner is subjected to a controlled annealingschedule, wherein the temperature of the glass is gradually reduced, toreduce internal stresses which develop therein during cooling. Ifunrelieved, these stresses can 8 cause the liner to crack duringcooling. The cooling schedule is described hereinafter.

MECHANICAL FINISHING After annealing, certain portions of the innerliner are partially trimmed. At this point, the liner may be inspectedfor flaws as it is still in the glass state. Subsequently, the liner 53will be heat treated in the manner described hereinafter to convert theglass to a crystallized, glass-ceramic material. The liner article maybe ground and polished to a desirable finish.

As is shown on FIGS. 18-20, annealed and inspected inner liner 53 ismechanically finished to rough shape. One operation shown on FIG. 18involves drilling the central barrel 54 of the piece so that it iscylindrical and extends vertically through liner 53. This is done bysuitable core drill 67. This also removes the webbing excess at 68 and69 in the part to finish the inside of the barrel 54 to the point shownon FIG. 19. The drilling also opens the passage of barrel 54 through thewall 71 at the push-up area 72 formed by the mold bottom plug 33 Next,the upper end excess of barrel 54 is removed by saw 70. The liner 53after being trimmed thusly is shown on FIG. 20. The steps of FIGS. 18and 19 may be interchanged. When this operation is finished, the liner53 is ready to be transferred to a kiln wherein the glass is convertedby heat treatment cycle to a crystallized, glass-ceramic part. Afterheat treatment is completed, the cavities in liner 53 may be ground andpolished by a tool such as an internal rotary grinder 73, shown on FIG.21.

GLASS COMPOSITION An exampleof a heat-crystallizable glass compositionused for forming a turbine liner as above described is the following,having this composition in parts by weight:

EXAMPLE I Ingredient Weight Percent SiO 74.8 M 0 7.l5 LI O 4.50 TiO, L45ZrO, L60 Sb O 0.30 Na,O 0.10 Molar Ratio SiO AI,O 7.40 Molar Ratio Li OM 0 0.90

The ingredients are mixed in a batch and are then heated in a glassfurnace and brought into the molten state and to a temperature ofapproximately 2,900F.; the molten thermally-crystallizable glassmaterial is then transferred to the mold apparatus, above described, andthe liner is formed.

FORMING PROCESS SCHEDULE mold at 0.83 and removed at 1.43. Concurrentwith the insertion of the pressing plunger at 0.83, the end mold membersare backed off by about one-sixteenth to oneeighth of an inch. After aninterval of about 1 or 2 seconds, the mold members are further movedabout by about an additional inch and the plunger is raised about 1inch. The separation of the mold members prevents the expanding metalmold from cracking the contracting cooling glass liner due to thedifferent coefficients of thermal expansion rates of the glass and metalmaterials. The backing off step should precisely compensate for thedifference in coefficients of thermal expansion of the glass and themold to prevent cracking the formed article. Table I, trials 2 and 3,show additional forming cycles:

Cooling water may be sprayed on the mold, or, with proper equipment, thecooling water can be circulated about the back (exterior) of the moldmembers. Surface temperature of the mold is maintained at less than1,000F.

COOLING SCHEDULE The formed glass liner article is cooled according tothe following schedule: The article is at about 1,250F. and is held forabout 6 hours. It is then cooled at a rate of 5F. per hourto aboutl,lF., and then at about 25F. per hour to room ambient temperature. Thiscooling schedule provided a satisfactory article which was free ofcracks and defects. At this point in the process, the article is clearand transparent, and is inspected for defects. This process provides atransparent article prior to the conversion to a glass-ceramic. If thearticle is defective, it can be rejected without further expensiveprocessing, including machining to dimensional tolerances. The cooledarticle is converted to a glass-ceramic according to a heat treatmentschedule.

HEAT TREATMENT SCHEDULE In one form, heat treatment was perfomied in atwostep series: t

STEP 1;

' rate of approximately 300F. per hour to room temperature.

Then, following Step 1, the article is subsequently processed asfollows:

STEP 2:

The article is heated at approximately 100F. per hour to about 1,300F.and held for approximately 8 hours; then approximately 10F. per hour toaboutl,420F. and held for approximately 100 hours; then approximately5F. per hour to about l,450F.: approximately 10F per hour to about1,600F. and held for approximately 10 hours; then approximately 10F perhour to about l,800F.; then approximately 5F. per hour to about 2,100F.and held approximately 4 hours; then approximately 5F. per hour to about1,950F., and approximately 25F. per hour to about l,500F.; and thendecreased at the rate of approximately 300F. per hour to roomtemperature.

Alternatively, heat treatment may be performed by omitting step 1 andfollowing the second step only.

Other heat cycles known in the art may be used for the cooling treatmentand also to convert the glassceramic forming material to a glass-ceramicso as to modify the end properties of the material, or to increase thespeed of the treatment.

The following is a description of other compositions of glass-ceramicmaking material used in the method of forming an article such as aturbine liner, by the process of this invention. Turbine liners operateat temperatures of at least 1,500F. and above and must be dimensionallystable, with very low coefficients of thermal expansion, and maintain amodulus of rupture of about 10,000 p.s.i., which is retained whenoperating at temperatures of at least 1,500F. over an extended period oftime.

Changes of length of less than 250 parts per million (p.p.m.), whenexposed to temperatures of at least 1,500F for a period of 2,000 hours,should be a property of any glass-ceramic component utilized in turbineliners and preferably, such change in length should be less than 100p.p.m with an ideal expansion being less than 50 p.p.m. at the abovetemperatures. Other examples of thermally crystallizable glasses, havingcertain narrow, critical composition limits, within the broad area of LiO-Al O -SiO and Li O-Al O -SiO -ZnO systems, when shaped into structuresincluding a turbine liner and then thermally in-situ crystallized to anat least partially crystalline ceramic (referred to herein asglass-ceramic) impart to the liner excellent thermal stability at hightemperatures of at least 1,500F. while simultaneously imparting a highmodulus of rupture. Furthermore, such structures have a coefficient ofthermal expansion within the range of i 3 X 10' /C. and some are withinthe range of i 0.5 X l0' /C. 0700C.

Thermally crystallizable glass compositions of the invention comingwithin the siO -Al O -Li O system consist essentially of the followingingredients present within the indicated ranges, expressed in weightpercent, and also within the indicated molar ratios.

wherein the nucleating agent is either TiO or a mixture of TiO with ZrOUsually, in order to obtain the desired properties, the compositionswill consist of 98-100 weight percent SiO A1 Li O the specan amount upto about 0.5 weight percent if such ingredients are deemed necessary forfining the glasses.

In one embodiment of the invention, the thermally crystallizable glasscomes within the following compoified nucleating agents. When the SiOJAlO molar sition ranges wherein the sole essential ingredients, ex-

ratio is from 4 to less than 5, the LEO/A1 0 molar ratio pressed inweight percent, are as follows, and whereln is from 0.75 to 0.97; whenthe SiO /Al O molar ratio the molar ratios are as lndlcated:

is from 5 to the molar ratio is from Ingredient Weight Percent to 0.97;when the SiO /Al O molar ratio is more than 7.5 and less than 9, thenthe Lip/A1 0 molar ratio is 1'35 5,, 3-

from 0.8 to 0.97; and when the SiO,jAl O molar ratio Ll,o' 3.5 6.5

is more than 9 and up to 10, the LEO/A1 0 molar ratio Nucleatng 3 9 isfrom 0.87 to 0.97. or

When the nucleating agent is a mixture of TiO wherein the SiO /Al Omolar ratio is from 5 to less ZrO Then the ZrO should not exceed 3percent and than 9. The nucleating agent is as defined above and,preferably should be less than 3 percent i.e., up to 2.8 when the SiO/Al O molar ratio is from 7.5 to less than TABLE II Composition No. l 23 4 5 6 7 8 9 10 11 510 78.30 78.90 75.85 76.45 74.80 73.00 70.85 70.8570.75 70.80 70.85 Al,o 14.20 13.65 16.10 16.20 17.15 18.45 20.05 20.0519.75 20.05 20.00 up 3.95 4.00 4.50 3.80 4.50 5.00 5.55 5.40 5.55 5.555.45 T10, 1.45 1.45 1.45 1.45 1.45 1.45 1.45 1.40 1.40 1.40 1.40 zro1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 v 1.60 1.60 1.60 sh,o 0.30 0.300.30 0.32 0.30 0.30 0.30 0.30 0.30 0.30 0.30 Na O 0.10 0.10 0.10 0.100.10 0.10 0.30 0.10 0.10 0.10 loo 0.20 Fo o1 0.45 0.10

Molar Ratio slo,/Al,o, 10.00 9.80 8.00 8.00 7.40 6.70 6.00 6.00 6.006.00 6.00

Molar Ratio Ll,o/Al,o 0.95 0.97 0.95 0.80 0.90 0.95 0.95 0.95 0.95 g0.95 0.95

Composition 510, 70.75 68.00 71.05 71.30 71.50 69.35 67.10 72.00 68.4564.00 64.85 Al,o 20.00 22.25 20.10 20.15 20.20 19.60 18.95 20.25 23.2525.35 25.60 up 5.35 6.20 5.30 5.00 4.75 4.55 4.45 4.20 4.75 7.10 6.00T10, 1.40 1.45 1.45 1.45 1.45 6.00 9.00 1.45 1.45 1.45 1.45 zro, 1.601.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 sl5,o 0.30 0.30 0.30 0.30 0.300.30 0.30 0.30 0.30 0.30 0.30 Na,o 0.50 0.10 0.10 0.10 0.10 0.10 0.100.10 0.10 0.10 0.10 K 0 R20,

Molar Ratio SiO,/Al,0 6.00 5.20 6.00 6.00 6.00 6.00 6.00 6.00 5.00 4.304.30

Molar Ratio l.i,o/Al,o,, 0.95 0.95 0.90 0.85 0.80 0.80 0.80 0.70 0.700.95 0.80

percent by weight and preferably at least 0.5 percent by 9, the LEO/A1 0molar ratio is from 0.87 to less than g t, and the total amount of z zis at least. 0.97; and when the SiO /Al O molar ratio is from 5 to 3weight percent unto ut 9 ght pe ce t. less than 7.5, the Li O/Al o molarratio is from 0.75

to 0.97. while more than about 9 Weight p t z or total Othercompositions and thermal crystallization of nucleating agent may beused, there Is no advantage In glass-ceramic forming-compounds aredisclosed in U.S. using 5119*! large amounts because the properties ofthe patent application, Ser. No. 146,664, Planchock et al, resultingglass-ceramics are not P Ya Further, filed May 25, 1971, commonlyassigned (the disclosure ralsing the T10 levels has the result ofralslng the therf hi h i i ated herein by reference, and forms malexpansion coefficient of the glass-ceramic. It is a part f hi li tiCritical to have at least 3 Weight Percent nucleating Representativecompositions for forming turbine linagent in the Composition when lessthan 3 Weight P ers of the invention are set forth in Table ll, whereincent total nucleants are present, the nucleation rate is th i gr di tare expressed in weight percents. so slow that the heat treatment cyclesare excessively This invention provides an apparatus and method for longand the strength of the glass-ceramic which is forming a one-pieceturbine inner liner from a glass formed is decreased. When ZrO ispresent in an convertible to a glass-ceramic. The compositions proamountof 3 weight percent or more, it raises the liquivide a turbine linerhaving very desirable characterisdus of the glass melt and makes moredifficult the protics of a high resistance to heat and a low coefficientof cessing of the glass into products. thermal expansion. The processhas another important advantage; the liner can be inspected for flawsbefore Refining agents, such as antimony tri-oxide, arsenic oxlde. orthe like, maybe present in the composition in continuing with theexpensive conversion of a glass to a glass-ceramic material.

Theinvention provides for a glass article of substantial mass andcomplex shape to be molded in a contiguous and integral construction.The apparatus and method of this invention provide for forming thiscomplex article of glass that is charged at molding at log viscosity of3 or less and provides the metal mold components including internalcoring elements that are forming sections of the mold. Internal coringand passages in the article formed thereby are later finished to shapeof the final configuration of the hardened glass article.

The finished article, having been annealed and inspected previously, isnow processed to convert the transparent, glassy state of the materialof the body to a glass-ceramic material of the properties being highlyadvantageous to use in a gas turbine or like utility.

I claim: 1

1. Apparatus for molding molten glass to form a complex article shape,such as a turbine inner liner article, comprising:

a. an elongated mold bed;

b. longitudinal mold guide means on said bed;

c. a pair of opposed end mold members supported on said bed and engagedwith said guide means for movement thereon toward and away from ajuxtaposed, molding position;

d. a pair of opposed side mold members;

e. means for pivotally mounting said side mold members on opposite sidesof the bed into and out of a juxtaposed, molding position in cooperationwith said pair of end members thereat;

f. said pair of side mold members, when in juxtaposed, molding position,partially enclosing said end mold members in an overlapping relationshipforming a mold cavity defining said complex article shape and having anopeningthereto for introducing the molten glass;

g. means on said bed and connected to the respective end mold membersoperable for separately moving each of said end members longitudinallyalong said bed; and v h.-forming means, operable through said opening tothe mold cavity for applying forming pressure to the glass loaded to themold cavity, thereby shaping such glass into said complex article shape.

2. The apparatus of claim 1, wherein the means (g) comprises a shaftconnected to each end mold member, a journal mounting on said mold bedrotatably supporting said shaft, thread means on said shaft, andcooperating thread means on said mounting, whereby rotation of the shaftimparts movement to the end mold member along said mold guide means onthe mold bed.

3. The apparatus of claim 1 wherein each of the end mold memberscomprises a mounting section and a forming section, said forming sectionincluding mold core elements adapted to shape hollow sections of saidcomplex article to be formed in the molding cavity, said mountingsection having a guide element engaging said mold guide means on themoldbed for aligning the forming section of each end mold memberlongitudiing block, the key means of each said mounting section engaginga slot of the positioning block when the forming'sections of the endmoldmembers are in molding position to provide a rigid support for theend mold members thereat, and a mold clamping device engaging each ofsaid side mold members in their molding position for clamping the moldclosed.

5. The apparatus of claim 4, wherein the longitudinal mold guide meanscomprises an elongated groove in said mold bed extending to the moldingposition for the end mold members positioned thereon, and a tongue oneach said mounting section of the end mold members engaging said groove,the tongue and groove guiding the opposed end mold members into theirmolding position.

6. The apparatus of claim 4, wherein the side mold members include anupper split neck section, the mold cavity opening being defined by saidupper neck section of the pair of side mold members when in moldingposition, the mold clamping device comprising a'torroidal cap memberencircling said upper neck section and clamping the latter in closed,juxtaposed relation.

- 7. Apparatus for molding molten glass comprising:

a. an elongated mold bed;

b. a plurality of movable mold members supported on said bed, includinga pair of end mold members;

c. each of said end mold members comprising:

d. a mold mount longitudinally slidable on said bed;

e. separate threaded shafts connected to each mold mount;

f. a journal means on said bed on opposite longitudinal ends of the endmold members rotatably mounting each said shaft;

g. means on said shaft for imparting rotation thereto in eitherdirection, the rotation of either said shaft imparting longitudinalmovement to the respective mold mount along said bed;

h. a key means positioned on both sides of the mold mount; and

i. a pair of positioning blocks connected to said bed,

one positioned on each side of the bed;

j.,said blocks having a slot for receiving said key when the end moldmembers are in a juxtaposed, molding position;

k. said positioning blocks and key being interengaged for stabilizingthe mold mount in the molding position.

8. Apparatus for molding molten glass to form complex articles, such asa turbine inner liner, comprising:

a. an elongated bed;

b. a pair of opposed endmold members;

c. a pair of opposed side mold members;

(1. means for mounting said end mold members for longitudinal movementon said bed to and from a juxtaposed, molding position;

e. means for mounting said side mold members for transverse pivotalmovement on said bed to and from a juxtaposed, molding position;

f. means on said bed connected to each said end mold member for movingthem into and out of the molding position, said side mold members beingmoved into molding position about said end mold members when in theirmolding position to overlap portions of said end mold members and definea mold cavity;

15 16 g. said end mold members having forming sections bers;

which comprise a mold core in said cavity when in c. means connected tosaid end mold members for mQldiT 1g Position; moving them relative toeach other between a h. said side mold members including upper necksecldi iti a d a non-molding position;

Hons definmg neck Qpenmg Connected to h 5 d. said juxtaposed side moldmembers overlapping mold cavity for introducing molten glass to the saidand partially abutting a portion of the juxtaposed end mold members insaid molding position; a pressmg plunger adapted for movement mm and eat least one of said pairs of molding members inout of said neckopening; and

eluding core forming elements which are disposed j. means mounting saidplunger opposite said neck opening at the molding position for movingthe latter into the mold cavity and press-form the glass in the moldcavity and form hollow interior sections of the article being molded insaid apparatus;

therein. and l l 9. Apparatus for forming molten glass, comprising: amold clamplng means POSltlOned about the p a. a pair of opposed,juxtapositioned side mold memportion of said side mold members forlocking said bers; mold members in the molding position.

b. a pair of opposed, juxtapositioned end mold mem- UNITED STATES PATENTAND TRADEMARK OFFICE CERTIFICATE OF CQRRECTIN PATENT NO. 3,819,352

DATED June 25, 1974 INVENTOR(S) 1 Yu K. Pei

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below: 0

Col, 8, line 43, should read Q Ingredient I Wegith Percent A1 0 3 l7 l5and Sealed this Twenty-eighth Day of June 1977 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner ofPatenlsand Trademarks UNITED STATES PATENT AND TRADEMARK OFFICE QETIFICATECECTIN PATENT N0. 1 3,819,352

DATED June 25, 1974 INVENTOR(S) I Yu K. Pei

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Col, 8, line 43, shouldread Ingredient Wegith Percent Sign: and Scaledthis A ttest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner uj'Paremsand Trademarks

2. The apparatus of claim 1, wherein the means (g) comprises a shaftconnected to each end mold member, a journal mounting on said mold bedrotatably supporting said shaft, thread means on said shaft, andcooperating thread means on said mounting, whereby rotation of the shaftimparts movement to the end mold member along said mold guide means onthe mold bed.
 3. The apparatus of claim 1, wherein each of the end moldmembers comprises a mounting section and a forming section, said formingsection including mold core elements adapted to shape hollow sections ofsaid complex article to be formed in the molding cavity, said mountingsection having a guide element engaging said mold guide means on themold bed for aligning the forming section of each end mold memberlongitudinally in molding position.
 4. The apparatus of claim 3,including a pair of positioning blocks mounted on the mold bed onopposite sides of said guide means, a key receiving slot in each saidblock, a key means carried on each said mounting section of the end moldmembers aligned with the corresponding respective slot of acorresponding positioning block, the key means of each said mountingsection engaging a slot of the positioning block when the formingsections of the end mold members are in molding position to provide arigid support for the end mold members thereat, and a mold clampingdevice engaging each of said side mold members in their molding positionfor clamping the mold closed.
 5. The apparatus of claim 4, wherein thelongitudinal mold guide means comprises an elongated groove in said moldbed extending to the molding position for the end mold memberspositioned thereon, and a tongue on each said mounting section of theend mold members engaging said groove, the tongue and groove guiding theopposed end mold members into their molding position.
 6. The apparatusof claim 4, wherein the side mold members include an upper split necksection, the mold cavity opening being defined by said upper necksection of the paiR of side mold members when in molding position, themold clamping device comprising a torroidal cap member encircling saidupper neck section and clamping the latter in closed, juxtaposedrelation.
 7. Apparatus for molding molten glass comprising: a. anelongated mold bed; b. a plurality of movable mold members supported onsaid bed, including a pair of end mold members; c. each of said end moldmembers comprising: d. a mold mount longitudinally slidable on said bed;e. separate threaded shafts connected to each mold mount; f. a journalmeans on said bed on opposite longitudinal ends of the end mold membersrotatably mounting each said shaft; g. means on said shaft for impartingrotation thereto in either direction, the rotation of either said shaftimparting longitudinal movement to the respective mold mount along saidbed; h. a key means positioned on both sides of the mold mount; and i. apair of positioning blocks connected to said bed, one positioned on eachside of the bed; j. said blocks having a slot for receiving said keywhen the end mold members are in a juxtaposed, molding position; k. saidpositioning blocks and key being interengaged for stabilizing the moldmount in the molding position.
 8. Apparatus for molding molten glass toform complex articles, such as a turbine inner liner, comprising: a. anelongated bed; b. a pair of opposed end mold members; c. a pair ofopposed side mold members; d. means for mounting said end mold membersfor longitudinal movement on said bed to and from a juxtaposed, moldingposition; e. means for mounting said side mold members for transversepivotal movement on said bed to and from a juxtaposed, molding position;f. means on said bed connected to each said end mold member for movingthem into and out of the molding position, said side mold members beingmoved into molding position about said end mold members when in theirmolding position to overlap portions of said end mold members and definea mold cavity; g. said end mold members having forming sections whichcomprise a mold core in said cavity when in molding position; h. saidside mold members including upper neck sections defining a neck openingconnected to the mold cavity for introducing molten glass to the saidcavity; i. a pressing plunger adapted for movement into and out of saidneck opening; and j. means mounting said plunger opposite said neckopening at the molding position for moving the latter into the moldcavity and press-form the glass therein.
 9. Apparatus for forming moltenglass, comprising: a. a pair of opposed, juxtapositioned side moldmembers; b. a pair of opposed, juxtapositioned end mold members; c.means connected to said end mold members for moving them relative toeach other between a molding position and a non-molding position; d.said juxtaposed side mold members overlapping and partially abutting aportion of the juxtaposed end mold members in said molding position; e.at least one of said pairs of molding members including core formingelements which are disposed in the mold cavity and form hollow interiorsections of the article being molded in said apparatus; and f. a moldclamping means positioned about the top portion of said side moldmembers for locking said mold members in the molding position.